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  1. #1
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    Default Help validate my understanding of DC and critique my intended setup

    First off, I've read through all the threads on DC and have learnt an amazing amount. I think I have exploded my brain three times over digesting it all! Thanks to everyone for the detailed contributions .

    The intent of this thread is not to capture everything perfectly (I couldn't do that if I tried) but to try and summarise in a simple way that captures the main points of consideration. I will no doubt screw this up, but I thought worth giving it a go for my own sake in gaining confidence that I understand what I think I know so far and that when I spend my $$$ soon on a DC setup, I am getting the most "real world" (not on paper) bang for my buck. I am ready for any feedback and apologies in advance if I make a mess of it!

    I'll break it into two parts - 1) my summary of DC and 2) what I am thinking to implement to get the best solution for the cost/effort that I can spare.

    My Understanding of DC

    Why Dust Collection?

    Dust Collection is really about two things:
    1. Collecting dust to keep the shed clean (visible dust) - let's call this visible clean. This is generally easy as we can see when it's working and when it's not - ie the visible dust is all over the shed or not.
    2. Collecting dust to keep the shed safe for our health (suspended and invisible dust in the air and on surfaces) - let's call this healthy clean. This is the hard one that most threads are focussed on. The crux being that majority of DC systems (your average 2HP DC, filtering mechanism such as dust bag or pleated filter, ducting, etc) fall far short of the minimum requirements to collect the harmful dust sufficiently the keep the shed air healthy. So in fact most people are working in a shed that is not a very healthy environment despite having all the gear.


    General Rules of Thumb to get the most from DC:


    • Collect as much as possible from the source - makes everything easier down the line
    • Place DC gear outside if you can. If not, put it in an airtight box and vent outside
    • Design efficient ducting (at least 6", smooth inner walls, no sharp turns, shortest runs possible)
    • Probably lots more I could list but will keep it simple for now


    The main factor in all the above is how much dust and what type you generate and how much time you spend in the shed. I don't know enough about the specifics here but my understanding is if you are working with power tools, particularly saw, sanders, jointers, then you will generate a lot of dust. Further, the materials you are working with can further exacerbate the hazard dust poses (eg: MDF is really bad).


    Mitigation Strategies:

    I have gathered the following as possible ways to mitigate:
    1. Buy top notch stuff that does what we want to out of the box (eg a Clearvue 3-phase unit) and make sure it's setup with appropriate ducting etc
    2. Buy usual stuff (eg 2HP Timbecon unit, maybe with a cyclone) and do a lot of modification work to get it up to spec (eg: expanding ports to 6", etc), and again ensure it's setup with appropriate ducting etc
    3. Buy usual stuff and leave it in it's stock state knowing that it won't be up to scratch, and then add additional gear to provide the mitigation, such as enclosures and extraction fans vented outside
    4. Either use power tools outside or just not worry too much about it, open up all the doors and windows and hope for the best!


    On the above three, my take is that (for each number listed above):
    1. Provides visible clean and healthy clean out of the box, but is very expensive and out of reach for manual casual sheds
    2. Provides visible clean out of the box and healthy clean via heavy modification of the DC gear. This modification is complex to get every aspect of it right and therefore a big risk of getting it wrong, and thus out of reach for most causal sheds (not to mention the time involved)
    3. Provides visible clean from out of the box DC gear and healthy clean using the principle of 20 room air changes per hour using non-DC gear. This is fairly easy and relatively cheap (cost of fans and bit of ducting to outside) and pretty easy to get right.
    4. Not particularly scientific but could be successful in terms of mitigation depending on your setup


    The one obvious mitigation strategy that is haven't yet mentioned that is easy and cheap is to wear a good quality, well-fitting dust mask at all times, or at the very least when using dust-producing machines and following their use until the room's are has been fully recycled.


    My Intended Setup

    Assuming my understanding of DC above is generally correct, I want to aim for number 3 in my above mitigation strategies. Given that, this is what I think is within reason for my setup given time (not much) and budget ($2k) constraints.

    Overview


    • Shop vac with blower function in some sort of enclosed box that vents outside, and a dust deputy between collection and vac
    • Stock standard 2HP DC situated outside in a sound proof box with a ducting system that does well with keeping the shed visible clean (and hopefully goes some way towards healthy clean)
    • Ventilation fans to create close to 20 room air changes per hour
    • Good dust mask for when using tools and take it off once above ventilation means it's generally safe (no idea how I will know but that's for later)


    Shed and Tools Info


    • Shed is approx 7.5m x 4m x 2.5m = 75m3
      • It is a single car garage and has car entrance at one end (obviously) and a doorway that leads outside at the other end
      • One note is the doorway outside is to an undercover carport that is enclosed on all sides but one, so it's not quite "outside", but fine for drawing fresh air through into the shed

    • Tools, the big ones I'm assuming I will one day end up with:
      • Table saw
      • Mitre saw
      • Thicknesser
      • Band saw
      • Router with table
      • Smaller powered sanders
      • Few other smaller tools


    DC Details

    Shop Vac Setup:
    • Likely a Ryobi 30L 1500w wet/dry vac (has a blower function) and a Dust Deputy
    • DD will keep most of the dust away from the vac itself
    • The dust that does make it to the vac will be vented outside using blower outlet
    • The other dust from motor cooling circuit will be captured by the enclosed box, which is also vented outside
    • By venting the box outside, it means it won't be portable so I will instead rely on a longer hose to connect to tools as needed
    • In the future, I could install permanent 50mm ducting for this, but not sure I need it at this stage


    DC Setup:
    • Likely this 2HP Sherwood model (https://www.timbecon.com.au/sherwood...dust-collector) with filter bags (not pleated filter)
    • You will notice it appears to already be built in the style that many of the modifications proposed on the forum talked about - namely that the impeller housing is connected directly to the separator, not via flex hose. However, it still has the issue of ports that are too small.
    • I will situate this outside the shed in a sound-proofed box (still need to read more about how to vent this box to the outside appropriately)
    • As for ducting for the DC, will stick as much as possible to the principles of smooth inner-walled ducting, short runs, no sharp turns
    • However, the idea of the DC is primarily to achieve visible clean at the source and go some way towards healthy clean, but acknowledging at this point that I'm not going to do any mods to improve it's performance. However, I can leave this turned on even when not using tools to act as a air circulator in addition to below if I want (but probably noisy and expensive to do, so not a regular thing)


    Forced Ventilation:
    • Get 12" version of this (4"/5"/6"/8"/10"/12" INLINE CENTRIFUGAL EXHAUST DUCT FAN Blower + Leather Jacket | eBay)
    • At 75m3, my shed needs to move 1500m3 each hour of air to get 20 room changes an hour
    • 12" does 1875m3 per hour as per specs, so assuming it's not that efficient, I'm hoping that's enough to remain above my 1500m3 required
    • I would mount this near the ceiling above the main car entrance, which is opposite the doorway and duct it straight outside
    • I think I'd just put some chicken mesh over the duct opening to stop critters getting in and to avoid baffles that would restrict air flow
    • EDIT: It's just occurred to me I don't know where I can get 12" ducting...so might have to go with 2 x 6" versions of this fan?


    Dust Mask:
    • Got one of those RZ masks. It fits really snugly and is comfy (for a mask)



    Rough Cost

    The rough cost of all the gear is $1500. I assume for ducting, materials for boxes, etc, it might top out at $2k. This is over what I had initially budgeted but given I want to be in the space for a long time I'm actually ok with it. As far as my health, I think that's a small price to pay if it actually works to minimise any impact to my health. I'll also have the kids in there one day and am very conscious of their health too.

    ----------------------------------

    Thanks for reading this far. I'm hoping some of you will weigh in with your thoughts and feedback. If I had to pose a few questions, they would be:
    1. Have I understood the main principles of dust collection correctly?
    2. Do you think my proposed setup is good given my $2k budget and not wanting to do much (if any) mods to the DC gear I buy?
    3. What would you do differently with the same time and budget constraints?


    But any and all feedback is welcome. And again, if I've totally missed the mark on this then feel free to let me know . Cheers

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  3. #2
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    Hi Lemery,

    As you may have suspected you are currently standing at the top of a very slippery slope.

    I think almost everyone who has contributed to the DE forum has at some time had a setup similar to what you described. Most of us then go on to improve as our needs grow.

    You seem to have a good grasp of the requirements in theory.

    I got the impression you will be buying the machines/equipment in stages. If so you could do well to modify your DE to 6" port when you get it. It is not hard to do. Then modify each machine as you add them into your setup. That will save you buying and tearing out 4" ducting to buy and add in 6" ducting later. It becomes a big job if you need to do 10 machines at once but its easy enough if you do it one at a time as you buy them.

    One thing that you didn't mention is what power is available in your workspace. Often it is very limited in a single car garage. By the time you run a 2hp dusty and a few exhaust fans you might not have enough power left for a tablesaw to make the dust you want to collect. Often a small garage might have two power points on a circuit it shares with half the house.

    Good luck with your journey.
    I got sick of sitting around doing nothing - so I took up meditation.

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  5. #4
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    Quote Originally Posted by doug3030 View Post
    As you may have suspected you are currently standing at the top of a very slippery slope.
    Yes I’m well aware!

    Quote Originally Posted by doug3030 View Post
    I got the impression you will be buying the machines/equipment in stages. If so you could do well to modify your DE to 6" port when you get it. It is not hard to do. Then modify each machine as you add them into your setup. That will save you buying and tearing out 4" ducting to buy and add in 6" ducting later. It becomes a big job if you need to do 10 machines at once but its easy enough if you do it one at a time as you buy them.
    Good point. I will buy in stages so perhaps not as big a job as you suggest. In which case, as you say, I can start with 6” ducting.

    Quote Originally Posted by doug3030 View Post
    One thing that you didn't mention is what power is available in your workspace. Often it is very limited in a single car garage. By the time you run a 2hp dusty and a few exhaust fans you might not have enough power left for a tablesaw to make the dust you want to collect. Often a small garage might have two power points on a circuit it shares with half the house.
    Another good point and it’s the other main area I’m reading up on a lot in terms of getting the space setup appropriately. In short, I have some budget to upgrade power to the garage if need be. It’s a place we’ve bought but not moved into yet so I don’t have the exact details of existing power setup. However, my rough thoughts on what would be ideal for me is to run a single larger cable (32A is what I’ve read as sufficient) to the garage and install a small breaker box in the garage. Then 2x 10A circuits for lights/chargers and tools. Maybe a 15A circuit as well but as of now I’m not planning on having any 15A gear, so could always install it later if need be (which should be easy with a breaker box already in the garage).

  6. #5
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    Lemerv,

    Firstly, congratulations on doing such a good job studying the problem and thinking deeply about a solution.

    No matter what dust collection system we choose, all of us are breathing dust at some time. Despite being very happy with dust collection in my shop, I know that under some circumstances I am breathing dust. What varies is the concentration of that dust and the exposure time. As BobL reminds us occasionally, Total Exposure = Concentration X Exposure Time. It sounds like you understand these things, and that, if we are wise, we do the best we can with the budget available to minimise the total exposure. If that is correct, you are on the right path.

    In a perfect world we would all be running something like a CV MAX with all machine ports/shrouds modified to optimise performance. We don't live in that world. Please bear in mind that when you are working at a machine with the set-up you describe, you will be breathing dust that the shop fans have not had a chance to remove because you only made it a couple of seconds ago. This would be my biggest concern.

    What would I do differently? Not sure. However I would consider seriously leaving the dusty in the shed and hooking it directly up to the machine in use. As I recall, BobL calculated that this approach, using a modified 2 HP dusty hooked directly to the Machine with 6 inch flexy, gave quite good capture at source.

    I should expose the fact that I am anal about capturing the dust at source, and that colours my thinking.

    Finally, when I was designing and installing my system BobL made it painfully clear that the greatest losses in airflow was not the ducting, it was the machines and hoods/shrouds themselves. My data has proven him correct. If you'd like to see how I did that, it can be found here Making 150mm DC ports for workshop machines

    You sound as if you are on the right path generally. Have fun!

  7. #6
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    Quote Originally Posted by John Samuel View Post
    Firstly, congratulations on doing such a good job studying the problem and thinking deeply about a solution.

    No matter what dust collection system we choose, all of us are breathing dust at some time. Despite being very happy with dust collection in my shop, I know that under some circumstances I am breathing dust. What varies is the concentration of that dust and the exposure time. As BobL reminds us occasionally, Total Exposure = Concentration X Exposure Time. It sounds like you understand these things, and that, if we are wise, we do the best we can with the budget available to minimise the total exposure. If that is correct, you are on the right path.
    Thanks John, good to know I'm heading in the right direction.

    Quote Originally Posted by John Samuel View Post
    In a perfect world we would all be running something like a CV MAX with all machine ports/shrouds modified to optimise performance. We don't live in that world. Please bear in mind that when you are working at a machine with the set-up you describe, you will be breathing dust that the shop fans have not had a chance to remove because you only made it a couple of seconds ago. This would be my biggest concern.
    This would be where I wear the dust mask and keep it on for a period of time after the dust creation stopped while the ventilation did its work. Not sure how long that should be though?

    Quote Originally Posted by John Samuel View Post
    What would I do differently? Not sure. However I would consider seriously leaving the dusty in the shed and hooking it directly up to the machine in use. As I recall, BobL calculated that this approach, using a modified 2 HP dusty hooked directly to the Machine with 6 inch flexy, gave quite good capture at source.

    I should expose the fact that I am anal about capturing the dust at source, and that colours my thinking.
    Interesting thought. Does that mean you have a mobile dusty to move near each machine? Or it's stationary but you have long flexy to reach everywhere you need? If it's the latter, does the length of flexy start to impact on overall performance vs smooth ducting from a stationary machine? In my case the dusty would be immediately outside the garage, so it would only add say 50cm to the overall length of ducting I require.

    Quote Originally Posted by John Samuel View Post
    Finally, when I was designing and installing my system BobL made it painfully clear that the greatest losses in airflow was not the ducting, it was the machines and hoods/shrouds themselves. My data has proven him correct. If you'd like to see how I did that, it can be found here Making 150mm DC ports for workshop machines
    Good to know. doug3030 is suggesting the same. I probably need to revisit this. However, I'm not sure how this works considering I have the ventilation fans doing 20 room air changes per hour? Would the gains from doing the 6" mods on everything be worth it if I am ensuring I get the 20 room air changes an hour? My thinking was stock standard DC setup plus the ventilation would produce a similar outcome in terms of visible clean and healthy clean?

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    Quote Originally Posted by lemerv View Post
    Good to know. doug3030 is suggesting the same. I probably need to revisit this. However, I'm not sure how this works considering I have the ventilation fans doing 20 room air changes per hour? Would the gains from doing the 6" mods on everything be worth it if I am ensuring I get the 20 room air changes an hour? My thinking was stock standard DC setup plus the ventilation would produce a similar outcome in terms of visible clean and healthy clean?
    If you decide to go with 4" ducting you might as well go with a 1 hp dusty. The extra HP will move very little extra air until you increase the size of the ducting too. a 2hp with 6" ducting moves three times more air (and therefore much more of the "health" dust) than a 2hp with 4" ducting. The difference is amazing
    I got sick of sitting around doing nothing - so I took up meditation.

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    The most important part of any system is the impeller size, you can have a 12" impeller driven by 50 horsepower and it won't move more than a 2 horsepower motor driving the same impeller.
    CHRIS

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    Quote Originally Posted by doug3030 View Post
    If you decide to go with 4" ducting you might as well go with a 1 hp dusty. The extra HP will move very little extra air until you increase the size of the ducting too. a 2hp with 6" ducting moves three times more air (and therefore much more of the "health" dust) than a 2hp with 4" ducting. The difference is amazing
    Ok that makes sense. Just to clarify and make sure I understand, this means everything (including machine ports) must be 6", correct? Ie 6" ducting stepped down to a 4" machine port is no good.

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    Quote Originally Posted by lemerv View Post
    Ok that makes sense. Just to clarify and make sure I understand, this means everything (including machine ports) must be 6", correct? Ie 6" ducting stepped down to a 4" machine port is no good.
    Sometimes it is good to go with 4" ducting. A good example would be to split the 6" duct into three 4" ducts to go to three collection sites on a bandsaw.

    Also, some machines are just too damn hard to fit a 6" outlet onto the so you can use the existing 4" port (usually after streamlining the flow a bit) and leave another 4" hose or two hanging in the air near the dustmaking site to scour the fine dust straight from the surrounding air. either way, run 6" to the machine and use it as one or divide it into two or better three to capture the maximum dust and maintain sufficient airflow through the system.
    I got sick of sitting around doing nothing - so I took up meditation.

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    Quote Originally Posted by doug3030 View Post
    Sometimes it is good to go with 4" ducting. A good example would be to split the 6" duct into three 4" ducts to go to three collection sites on a bandsaw.

    Also, some machines are just too damn hard to fit a 6" outlet onto the so you can use the existing 4" port (usually after streamlining the flow a bit) and leave another 4" hose or two hanging in the air near the dustmaking site to scour the fine dust straight from the surrounding air. either way, run 6" to the machine and use it as one or divide it into two or better three to capture the maximum dust and maintain sufficient airflow through the system.
    Perfect, thanks. You answered my follow up question, which was around keeping the 4” port on the machine and leaving another two 4” hoses hanging free.

    In the above scenario, is it ok for the total inlet to be more than the 6” cross-sectional area of the ducting? Or better to make the inlets equal exactly the cross-sectional area of the ducting? (In which case for 6” ducting the combo would be 2 x 4” inlets plus 1 x 2” inlet.)

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    Quote Originally Posted by lemerv View Post
    In the above scenario, is it ok for the total inlet to be more than the 6” cross-sectional area of the ducting? Or better to make the inlets equal exactly the cross-sectional area of the ducting? (In which case for 6” ducting the combo would be 2 x 4” inlets plus 1 x 2” inlet.)
    Cross section area is a guide but not exact. Very little is exact, particularly if you don't have BobL's measuring gear.

    When you go from 1 x 6" to 3 x 4" you get a bigger cross section but that does not necessarily indicate more capacity because you also get a massive increase in wall surface area which equates to extra friction resulting in less flow.

    To exacerbate this, often the 6" is sewer pipe (smooth walls) and the 4" is corrugated (because it has to bend around the machine to fit to the multiple ports), meaning more turbulence restricting the flow.

    1 x 6" branching to 3 x 4" is fine.

    Don't even bother with 2" pipe unless you are running it to a vaccum cleaner.
    I got sick of sitting around doing nothing - so I took up meditation.

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    Quote Originally Posted by doug3030 View Post
    Cross section area is a guide but not exact. Very little is exact, particularly if you don't have BobL's measuring gear.

    When you go from 1 x 6" to 3 x 4" you get a bigger cross section but that does not necessarily indicate more capacity because you also get a massive increase in wall surface area which equates to extra friction resulting in less flow.

    To exacerbate this, often the 6" is sewer pipe (smooth walls) and the 4" is corrugated (because it has to bend around the machine to fit to the multiple ports), meaning more turbulence restricting the flow.

    1 x 6" branching to 3 x 4" is fine.

    Don't even bother with 2" pipe unless you are running it to a vaccum cleaner.
    Thanks. Will take all this into account.

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    This is instructive as I haven't show it for a while

    The horizontal axis is pressure in "column inches of water".
    A typical 2HP DC produces a maximum of about 8" - see red arrow on horizontal axis
    The vertical axis is air flow in cubic feet per minute (CFM)
    The red lines are ducting diameters in inches.

    The intersection of the 8" pressure vertical with the 4" duct line (blue dot) traces horizontally to the LHS axis shows 400 CFM.
    The intersection of the 8" pressure vertical with the 6" duct line (green dot) traces horizontally to the LHS axis shows ~1150 CFM.
    The flow rates pretty well coincide with what I've measured.

    Flowratesxp.jpg

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    Quote Originally Posted by BobL View Post
    This is instructive as I haven't show it for a while

    The horizontal axis is pressure in "column inches of water".
    A typical 2HP DC produces a maximum of about 8" - see red arrow on horizontal axis
    The vertical axis is air flow in cubic feet per minute (CFM)
    The red lines are ducting diameters in inches.

    The intersection of the 8" pressure vertical with the 4" duct line (blue dot) traces horizontally to the LHS axis shows 400 CFM.
    The intersection of the 8" pressure vertical with the 6" duct line (green dot) traces horizontally to the LHS axis shows ~1150 CFM.
    The flow rates pretty well coincide with what I've measured.

    Flowratesxp.jpg
    Thanks BobL. That is a massive jump in flow rate. It’s a bit counterintuitive at first glance because on the face of it the jump from 4” to 6” doesn’t seem that much. But in terms of cross-sectional area the 6” is about 2.25x bigger than the 4”.

    Well, I’m off to read the threads on modifying the DC to be 6” as it seems from all the feedback this will be well worth it.

    Side note - why the @$#* don’t they just make them with 6” fittings? Seems a small amount of design change for a huge benefit. My guess is something to do with cost…but still, seems silly.

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